Lamp-socket.



D. WOODHEAD.

LAMP SOCKET.

APPLICATION FILED MAR. 16| 1917- RENEWED FEB. 18.19I8l 1,265,285. Patented May 7,1918.

2 EETS-SHEET l.

D. WOODHEAD.

LAMP SOCKET.

APPLICATION FILED MAR. I6. |917. RENEWE'D FEB. 18. 1918.

1,265,285. Patented May 7,1918.

2 SHEETS-SHEET 2.

' DANIEL woonnEAn, ornvAnsToN, ,ILLINoIs LAMP-SOCKET..

.Specication'of Letters Patent.

Patented May 7,1918.

'Application nled March 16, 1917, Serial No. 155,312. Renewed February 18, 1918. Serial No. 217,993.

- general object of the invention is to provide a simple and efficient socket of this character.

In carrying out my invention, I employ a helical spring into which the threaded lamp base screws. This spring frictionally grips the lamp base when an attempt is made to unscrew it, and'the lamp will remain locked in the spring unless the outer end of the spring is held in such manner as to prevent the gripping action. I inclo'se the spring in a housing whichprevents anyone from gaining access to the end. of the spring to hold Vit. I so construct the spring and housing,

however, that by a series of proper and quasi secret manipulations on the lamp bulb in the hands of the operator, the housing and spring may be caused' to inter-engage and thus hold the spring against performing its gripping and locking function. l

I accomplish my object by the construction illustrated in the accompanying drawings, in which:

Figure 1 is an axial section of the lamp socket taken on the line 1,-1', Fi 2.

Fig. 2 is an axial section on the ine 2 2, Fig. 1.

Fi 3 is a view partly in axial section 1 showlng the manner in which. the pron on the end of the spring may be brought into engagement with the notch or pocket in the housing to permit the lamp to be removed. Fig, 4 is a transverse section on the line i-arig. 2. f

Fig. 5 is a perspective View of the socket and bulb showing the same in the positions normally occupied when in use. Fig. 6 is similar to Fig. 5 but shows the prong engaged in the notch or pocket.

Similar numerals referto similar parts throughout the several views. y

In the form selected to illustrate the invention, the socket has a housing 1 of por.- celain or other suitable insulating material.

-It is fastened to an insulating base 2 by screws 3, 3, which are suitably connected to supply conductors 4, 5. One of these screws is` in electric connection with the center terminal 6, and the other with a shell 7 to which the inner end of a helical spring 8 is fastened. Thus, the center terminal 6 and spring 8 are electrically alive and are insulated from each other. When in position in the socket, the center lamp contact 9 engages terminal 6 and the metallic shell 10 (which forms the outer contactfof the lamp) engages the spring 8. `Said spring is also right handed; that is, it progresses inward toward the back ofthe socket when traced in a clockwise direction.v The back of the closely surrounds the spring and extends .somewhat beyond its'outer end.-

The outer end of the helical spring has an arm 12 formed upon it. This arm extends outward approximately radially and forms a prong which extends into the annular chamber 13 formed on the inside of the housing. Ordinarily, the different turns of the spring will lie more or less closely together when the lamp base is absent; but screwing the base into the spring will distend the latter and move the turns somewhat farther apart. The width of the chamber 13 is great enough to accommodate the prong both when the lamp base is absent and when present.. Communicating with chamber 13 at a point remote from the normal position of prong 12 when' the lamp base is in place, is a pocket or notch 15 for receiving and retaining'the pron Commercial lamp bulbs having screw threaded bases are practically all made with right handed threads, so that when the lamp'` is being screwed intcthe socket it will be turned in a clockwise direction. Assuming that lamp bulbs having the usual right handed thread on their bases are to be employed, pocket l5 is angularly offset in a clockwise direction from the normal posi- 'when the lamp base is screwed into the spring 8, the latter will frictionallyengage it but not suficiently to grip it and prevent the bulb without holding the free end of the spring back and preventing the spring from wrapping itself too tightly around the lamp base. In my device, however, the housing is longer than the spring; that is, it projects outward beyond the point reached by the outer end of the spring. Hence it is impossible for any person to hold back the -end of the spring with his ngers or any ordinary tool. Consequently, the lamp is locked in place and is non-removable to all persons except those who know just how to manipulate the device. -To the person who is informed, the manner of release is simple. The method is to first rotate the lamp in a clockwise direction; that is, in the direction q, to `screw the lamp farther into the socket.

This brings the prong opposite the pocket 15, whereupon'the operator pulls the lamp toward him and causes the prong to enter the pocket. He then rotates the lamp bulb in an anticlockwise direction, taking care to exert constantly an outward pull to keep the prong in the pocket. Hel continues this action until the lamp base is finally released. The prong thereupon immediately springs out of the pocket and also swings angularly away from it. Usually the angular distance between the prong and the pocket will be greater when the lamp base is absent than when present, but the parts are so constructed that' in any event the prong cannot be brought opposite the pocket without being forcibly rotated through a greater or smaller angle, according to design.

It will be evident from the foregoing that three'distinct movements are necessary in order to remove the lamp from the socket. The first movement is to rotate the lamp in the opposite direction to the one finally required to unscrew the lamp. Second, the lamp must be pulled outwardlyl to seat the prong in the pocket, and third, a reverse rotation must .be imparted while the prong continues to be forcibly held in the pocket. Thus with m'y device, the preliminary movement in removing the lamp is to rotate it in the direction exactly opposite to the one which would be naturally expected. It is very unlikely therefore, that any unauthorized person would accidentally hit upon the program of operation necessary to remove the lamp. It will be noted, also, that it is not suiicient to accidentally bring the prong momentarily into the pocket. .It must be maintained there, against the pressure of thel spring, for all or practically all of the time that the lamp is being unscrewed. If the person should at any time permit the prong to leave` the pocket, it would be necessary for him to again impart a clockwise rotation and a pull before he can continue the necessary anti-clockwise rotation. And it is not sufficient to merely rotate the lamp in a clockwise direction. The end of the spring itself must be thus rotated and ordinarily if the lamp has been part way unscrewedthere will not be suicient friction between the lamp base and the spring to rotate the'springin a clockwise direction. Consequently, if the operator once lets the prong escape from the pocket he cannot get it back in again without screwing the lamp base back in again, either to the limit or until it creates enough friction to enable it to force the prong back again to vthe pocket. The device, therefore, requires not only a moderate amount of skill in manipulation, 4

but at least one or two of the three separate motions required are unnatural and therefore unexpected, and therefore not likely to occur to the average person.

In the accompanying drawings, especially Figs. 5 and 6, I have, in order to better explain the principle of operation, shown the housing somewhat wider at the mouth than it is in practice. In the commercial construction, the housing approaches vmore closely to the lamp base and, being opaque, effectually hides the ron'g and pocket, at least to an extent sucient to prevent lthe proper method from becoming apparent. It

is obvious, of course,V that the housing may be made quite close fitting and may be lengthened to such an lextent as to render the` vital parts of the deviced invisible. l Having thus described my invention, what I claim as new and desire to secure by Letters Patent, is i 1. A socket for electric bulbs having housing and a helical gripping spring in said housing into which the base screws, the inner end of the spring being fixed, and the housing having a shoulder for engaging the free outer end of the spring to permit unscrewing of the bulb, the shoulder being nearer the mouth of the housing than the free end of the spring is when the bulb is in place, whereby the operator must pull on the bulb and stretch the spring axially before the end of the spring willgengage the shoulder.

2. A device of the character described having a socket, a helical spring Vtherein fastened at the inner end to the socket, said spring being adapted to have the base of an electric bulb screwed into it, and a shoulder formed in said socket. for engaging the free end of the spring, said shoulder being both mamas angularly and axially remote from the position which the free end of the spring normally occupies when the bulb is in place.

3. A lamp socket having a housing, a coiled spring therein into which the lamp base screws, the inner end of the spring being fast in the housing and the outer end having a prong, and a pocket in the housing for engaging said prong, said prong being normally angularly offset from said pocket whereby the outer end of the spring must be rotated before the prong can be brought into the pocket.

4. A lamp socket having a housing, a helical gripping spring therein into which the lamp base screws, the inner end of the spring4 being fast in the housing and the outer end having an arm projecting outward, approximately radially, the lspring being distended by the lamp base when the latter isin position, the housing having a pocket for receiving said arm, said pocket being angularly at the left of the normal position of said arm when the lamp base is Ain position, whereby'the operator must, to

bring the arm into the pocket, rst turn the lamp base a short distance to the left or in the same direction that he would in screwing the lamp base into the housing. X

5. `A lamp socket having a housing, a

coiled spring in said housing into which the` lamp base screws, the inner end of the spring being fastened in the housingand the outer end having a projection, the housing-.having a pocket for engaging said projection to prevent the spring from gripping the lamp base and preventing removal thereof, the pocket being farther from the inner end of the spring than the projection normally is, whereby the operator must pull outwardly to bring the projection into'the pocket.

6. A lamp-socket having a helical grip- "ping spring intov which thelamp basescrews,

a housing containing said sprlng and proj ecting beyond the outer end thereof, a prong '45 on'l the outer end of the spring, the hous' having an internal pocket for receiving an engaging said prong, the pocket being angularly offset and farther out thanthe normal position of the prong, whereby the operator must both rotate the prong and pulloutwardly to bring the prong into the pocket.

than the prong normally is whereby the 6o operator before unscrewing. the lamp` must first pull on it and rotate it in a clockwise direction as he wouldin screwing the lamp in.

8. A locking socket for electric bulbs, the socket having a housing closed at the side `and inner end, a helical 'ppin sprin in said housing into whic the amp ase screws, the inner end ofgthe spring being secured in the housing and the outer end being free, whereby the spring may be distended when the lamp base is screwed into it, the free end of the spring having a prong projecting outward approximately radially and the socket having a chamber on the inside for accommodating thesaid prong and a notch communicating with said chamber for receiving and engaging said prong, the notch being farther, from the inner end of the housing than the prong normally is when the bulb is in place.

In witness whereof, I have hereunto subscribed my name; j DANIEL WOODHEAD. 

